Stand up an Eclipse Mosquitto MQTT broker and design pub/sub topics for industrial telemetry

Steps

1. Add an explicit listener directive to mosquitto.conf (e.g. listener 1883) — without it, a default install only accepts connections from localhost
2. Require authentication with allow_anonymous false plus password_file, generating entries with the mosquitto_passwd utility
3. Design a hierarchical topic tree with consistent segments, e.g. plant/line1/sensor7/temperature
4. Publish telemetry with mosquitto_pub -h <host> -t 'plant/line1/sensor7/temperature' -m '<value>'
5. Subscribe with mosquitto_sub -h <host> -t 'plant/line1/+/temperature' -v (+ = single-level wildcard, # = multi-level)
6. Restart or reload the broker after editing mosquitto.conf for changes to take effect